The present invention relates in general to apparatus for manipulating paper signatures or objects of like nature. More particularly, the invention pertains to apparatus for performing a given operation upon individual signatures in sequence but with the signatures efficiently brought in and taken out at extremely high rates in terms of signatures per unit time.
Although the invention in certain aspects is not so limited, it is aimed toward achieving, and is embodied in, a high speed quarter folder. As is known in the printing art, newspaper presses conventionally include folding and transport units which bring out multiple sheet, single folded assemblies in an overlapped running shingle. The assemblies are called "signatures" and their folded edges are called "spines". The signatures in a running shingle usually move with the spines as leading edges and with each signature set back slightly (here called the shingle setback SSB) from the one which precedes it so that they travel in overlapped relation. A single fold signature may sometimes be called a "half signature"; when it is folded again about a medial line perpendicular to its spine, it becomes a quarter signature. By cutting at the original spine edge, a quarter signature may be turned into a booklet wherein each page is one quarter of an original sheet of paper. A quarter folder makes the second fold in a half signature to convert it into a quarter signature.
Almost universally, half fold signatures exit from a printing press, or they come from any other source, as a running shingle--for the reasons that the shingle is less flexible than individual signatures, and a high rate of through-put in items per unit time (e.g., signatures per hour) can be obtained with a lower conveyor speed in comparison to transporting signatures spaced out to travel one at a time.
When a given operation, such as quarter folding, must and can only be performed on signatures one at a time, however, then a spaced-out stream of successive signatures is required. And the conversion of a shingle to a stream has heretofore been a limiting factor on the through-put rate--to such an extent that quarter folders and similar devices could not keep up with, and could not directly accept the running shingle output of, a high speed press or other high rate source of half signatures. Indeed, this limitation has resulted in a common practice of stacking half signatures coming from a printing press, storing them, and subsequently feeding them into a slower speed quarter folder or similar "one at a time" machine.